package com.tanhua.server.interceptor;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.tanhua.common.utils.Cache;
import org.apache.commons.codec.digest.DigestUtils;
import org.apache.commons.lang3.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 拦截器（缓存）
 */
@Component
public class RedisCacheInterceptor implements HandlerInterceptor {

    @Value("${tanhua.cache.enable}")
    private Boolean enable;

    @Autowired
    private RedisTemplate<String, String> redisTemplate;

    @Autowired
    private static final ObjectMapper MAPPER = new ObjectMapper();

    @Override
    public boolean preHandle(HttpServletRequest request,
                             HttpServletResponse response,
                             Object handler) throws Exception {

        // 缓存全局开关的校验
        if (!enable) {
            return true;
        }

        // 校验handler是否是HandlerMethod
        if (!(handler instanceof HandlerMethod)){
            return true;
        }

        // 判断是否是get请求、
        if (!((HandlerMethod) handler).hasMethodAnnotation(GetMapping.class)){
            return true;
        }

        // 判断是否加了@Cache 注解
        if(!((HandlerMethod) handler).hasMethodAnnotation(Cache.class)){
            return true;
        }

        // 缓存命中
        String redisKey = createRedisKey(request);
        String cacheData = this.redisTemplate.opsForValue().get(redisKey);
        if (StringUtils.isEmpty(cacheData)){
            // 缓存未命中
            return true;
        }

        // 缓存命中 将data数据进行响应
        response.setCharacterEncoding("UTF-8");
        response.setContentType("application/json; charset=utf-8");
        response.getWriter().write(cacheData);

        return false;
    }

    /**
     * 生成redis中的key 规则：SERVER_CACHE_DATA_MD5(url + param + token
     *
     * @param request
     * @return
     */
    public static String createRedisKey(HttpServletRequest request) throws Exception{
        StringBuffer url = request.getRequestURL();
        String param = MAPPER.writeValueAsString(request.getParameterMap());
        String token = request.getHeader("Authorization");

        String data = url + "_" + param + "_" + token ;

        return "SERVER_CACHE_DATA_" + DigestUtils.md5Hex(data);

    }
}
